Novak Djokovic is dragging his body to the starting line not far from the Greenwich meridian with his usual disregard for the weight of time. At 24, he is young enough to laugh at the burdens tennis has already imposed on his lean body, and old enough to recognise he will not be able to do so much longer.

Reminded that Bjorn Borg had said recently it was his own excellence in being able to reach so many finals that persuaded him to retire at 26, the world No1 smiled. "It is a busy schedule, I'll tell you that," he said, as the second group of four players among the world's best eight gathered at the O2 Arena on the eve of the Barclays ATP World Tour Finals.

"Players are having a lot of difficulties, especially towards the end of the year, to be fit and ready to perform 100% in each event. But, if I have the results that Borg had I might be stopping in a couple of years as well. I would be more than happy to have his career.

"For sure, it is a subject to be discussed. You could see at the US Open this year, many players complained. We have to understand how the tennis world works and how it has been working for many years. I think we need to be open for changes. It's a different time. With all the respect for the tennis 20 years ago, tennis today is much more physical and takes away lots of energy from our bodies. We don't get much time to recover."

The Serb was not a member of the militant faction of Andy Murray, Rafael Nadal and, to a lesser extent, Andy Roddick, who threatened industrial action in New York in pursuit of a kinder schedule, but said: "It's not that easy but, yes, most of the players agree to have a little bit shorter schedule."

As for Murray, who is in his section of this round-robin finale to an 11-month slog on the circuit, Djokovic views the Scot's striving for a first grand slam with more equanimity than those who write the stories and headlines agonising over the lack of British success at the summit of the game. Murray plays David Ferrer on Monday afternoon, while Djokovic goes against Tomas Berdych in the evening.

"It's very hard for me to speak for him," he said, "but I know the difference in my game was just that mental approach and maturity on and off the court, as a person as well – just figuring out things, how to do deal with the pressure, how to play the right shots at the right moment, using the experience I have had over the years playing Roger [Federer] and Rafa.

"My game is more or less the same, but it's that mental switch, the self-belief that I can win the matches I have been losing in past years. Andy has played a few grand slam finals already and he's been in the top four in the world the last couple of years, so I'm sure that he wants a grand slam title at this moment more than anybody. I'm sure he will make it because he has the quality to do it. He has won so many big events, he has won against all the best players in the world.

"He's a complete player. He can perform well on this surface as well as all the other surfaces. That gives him enough reason to believe he can do it."

But what about that right arm that has dangled painfully by Djokovic's side in recent months, not to mention strains on the rest of his body that have cut him down this season: is this a tournament too far? "A couple of weeks ago I had an injury of the abdominal muscles but it's all coming well now. I have been serving at 100% the last two or three days. So, for me, the shoulder is fine at this moment. I can say it's recovered and I'm ready to compete."

The key words, three miles down the road from the place the clocks start ticking, were "at this moment".